The broad objective of this project is an understanding of the basic metabolism of gastropod vectors of animal parasites as it relates to their biology and the biology of the intermediate stages of the parasites they harbor. The specific objectives include an elucidation of their cellular mechanisms for amino acid catabolism and detoxication of the ammonia consequently released. Enzyme characterization and localization are being done in aquatic, terrestrial and amphibious snails. Those enzymes of special interest are the transaminases, glutamate dehydrogenase, glutamine synthetase, carbamyl phosphate synthetase, glutaminase, enzymes of the purine nucleotide cycle, and L- amino acid oxidases.